Boeing has increased its estimate of the operating performance of the 737 Max, saying the re-engined narrowbody will burn 14 percent less fuel than the current 737NG consumes. In July, the manufacturer said the 737 Max with new CFM Leap-1B turbofans will be 13 percent more fuel efficient.

In a teleconference on Tuesday, Boeing executives provided a program update based on the completion of final aerodynamic, engine and weight audits for the 737 Max, which the company expects will enter service in the third quarter of 2017. Boeing has more than 1,600 orders for the aircraft.

Since locking down a firm configuration in July, “we now have a key understanding of what the airplane is going to be. We’ve gotten more mature data, and we’ve retired a lot of uncertainty around the performance projections,” said Keith Leverkuhn, 737 Max program manager. “Based on that configuration, the good news is that we can now promise our customers a 14-percent improvement over today’s fuel-efficient 737…That’s really at the typical ranges that a lot of 737 customers currently fly. When we fly even longer ranges, closer to 3,000 nautical miles, that number is actually going to look more like 15 percent improvement in fuel use.”

Michael Teal, 737 Max chief project engineer, said half of the 1-percent gain in fuel savings over Boeing’s previous estimate comes from an aerodynamic improvement that is realized when integrating the new engines and nacelles to the wing. He attributed the other half-percent gain to a combination of new winglets and final propulsion system performance calculations.